Mineral acid salts of cationic surfactants derived form the condensation of fatty acids and esterified dibasic amino acids and their use for the preservation of foodstuffs are known in the prior art—see, e.g., U.S. Pat. Nos. 5,780,658, 7,087,769 and 7,407,679. A useful cationic surfactant is the ethyl ester of lauramide-arginine (hereinafter referred to as the ethyl ester of Nα-lauroyl-L-arginine); such ester is also referred to herein by the term “LAE”. The anions of such mineral acid salts are typically Br−, Cl− or HSO4−, with the most typical being Cl−.
It is also known in the prior art to prepare organic acid salts rather than the mineral acid salts of the cationic surfactants. WO 2007/014580 discloses that such organic acids may be, e.g., citric acid, lactic acid, acetic acid, fumaric acid, maleic acid, gluconic acid, propionic acid, benzoic acid, carbonic acid, glutamic acid or other amino acids, lauric acid and fatty acids such as oleic acid and linoleic acid.
It has been found that the organic acid salts of the cationic surfactants, rather than the mineral acid salts of the cationic surfactants, are especially useful for the preservation of foodstuffs. However, the process for preparing the organic acid salts disclosed in WO 2007/014580 leaves a lot to be desired. The yields are poor and moreover, the product is impure. For example, in the case of LAE being converted from the monohydrochloride salt to the acetate salt, the product is contaminated with a significant amount of the byproduct Nα-lauroyl-arginine (“LAS”) acetate.